Lead alloy



Aug. 29, 1939. B. JONES 2,171,180

LEAD ALLOY Filed Feb. 24, 1957 Patented Aug. 29, y1939 LEAD ALLOY Brlnley Jones, Perivalc, England, assigner toA 61001113.55 Wall & Lead Industries Limited, L01!- don, England Application February 24, l1937, serial No. 127,470

In Great Britain June 4, 1936A y 7 Claims.

'Iliis'invention relates to alloys of lead and telf lurnlm containing copper.

In Britishjspeclcation No. 414,606 are describedgralloys of this nature containing a. pro- .5 portion of from Q01-0.1% of tellurium and 01015% vof copper, it being stated that the incorporation -of the tellurium and the copper in the alloy conjointly imparts to the alloy a greater resistance to corrosion than an equivalent 10 quantity of either oi these elements separately. Extruded products such as cable /sheathi-ngs or sometimes pipes are often manufactured on a plant which operates with a 'die havi'ng a bridge core. e Here it is necessary toextrude at a temperature high enough for the metal to weld together again beyond the bridge core, and the .optimum extrusion temperature from this point of view is relatively high, for example, a temperature as close to the melting point of lead (327 C.) as is practicable. On the other hand,

the optimum extrusion temperature of leadtellurium alloys `from the point of view of the grain structure of the extrudedV product is considerably lower. f 4 .I have found that as the proportion of copper -present uin the alloy is increased, the tendency to develop a coarse grain when extruded at Ia high -temperature is progressively diminished.

of ve, of an etched cross section of a hot extruded pipe made from an alloy of lead containing 0.05% tellurium but no copper,

Fig. 2 is a similar view, at the same magnication, of a hot extruded pipe made from an alloy 1 of lead containing 0.05 tellurium and 0.067%

' copper,

- tion.

Useful results are obtained with a copper con- A tent as low as 0.03%, but it is preferred to keep the copper content within the range of 0.05-0.1%. Particularly good results are obtained when the 40 tainscopper, the metal can be extruded at a suflic'iently vhigh temperature to avoid weaknesses due to inadequate welding .together of the metal beyond the bridge core, but at the same time the product retains a fine grain, which re- -45 -sults in ithaving far superior mechanical properties, and Ain particular a greatly improved resistance tointercrystalline cracking. Also, provided the copper content is above 0.06%, the

metal can be subjected to loca'l welding where desired without impaired. g

The invention will nw be described in further detail with reference tothe accompanying drawing, in which y' Fig. 1 is a photomicrograph, at a magnication the fine grained -st'ructure being grain can be made by hot extrusion from cop- Fig. 3 is a diagrammatic sectionaly view illustrating the segregation which occurs in a casting made from a lead alloy containing 0.05% tellurium and 0.08% copper,

Fig. 4 is a side elevation, partly insection, of a bridge core pipe, press,

Fig. 5 is an enlarged sectional view of the bridge core of this press, and

Figs. 6 and 7 show respectively av pipe and a cable sheathing.

When manufacturing extruded products, such as pipes or cable sheathingfromlead alloys, it is generally desirable to extrude the metal at g as high a temperature as practicable from considerations of speed and convenience of opera- This is particularly so in vthe case of a bridge core press, where, the metal has to weld together again beyond the die. y

In the case of binary alloys of lead and tellurium, it is found that the metal recrystalizes with 'a ne grain when-it is extruded at a relatively low temperature, so that the material has' improved mechanical properties as compared with extruded soft lead which recr'ysta'llizes with a coarse structure. Binary tellurium-lead alloys cannot however -be extruded at the high temperatures customary lfor ordinary 'soft lead becase under these conditions the cast structure 35 is not completely broken down. A1 structure such as that shown in Fig. 1 develops, with the resultthat insuillcient ductility is obtained. Consequently it has been necessary toextrude binary lead" and tellurium alloys at lower temperatures than those which are ordinarily employed for soft lead. Copper tellurium lead alloys extruded at' a high temperature possess a very much ner grain than binary tellurium-lead Aalloys which have been extruded at the same temperature. This isfshown in Fig. 2.' 'Ihe result is that the product has improved mechanical properties, inparticular an improved ductility as compared with the product shown in Fig. t 1. The critical lower limit of 0.06% copper is not decisive as to the grain sizeof the metal after extrusion, as it isin the case of Welding., and pipes and cable sheathings of reasonably ilne per-tellurium-lead alloys containing as little as 0.03% copper.

It is preferred to keep the copper content below 0.07%, as 4otherwise some tendency towards segregation is observed, as may be seen from Fig. 3 where the excess copper is indicated at A, having segregated to the top of thcasting. It will be appreciated that this ligure is 'diagrammatic only, the segregated copper being shown, for the sake of clarity, on a greatly enlarged scale. The copper content can however be increased to 0.1% without the effects of segregation becoming serious.

The present invention has particular advantages when applied to the manufacture of pipes on a bridge core press. Such a press is shown in Figs. 4 and 5.

It comprises a container 20'v mounted on a hydraulic ram, which is operable to raise the container so that it passesv over the lower end of a xed hollow ram .2|, which fits exactly within the container. Across the lower end of the ram 2| extends a removable bridge member 22 carrying an upright core 23.

The container is ilrst lowered and filled with molten metal. It is then raised with the result that a hollow tube 2li of metal is extruded between the Core 23 and the co-operating die 25. This constitutes the pipe shown separately in Fig. 6.

With such a press, it is clearly desirable to extrude. the metal at as high a temperature as possible, in order to ensure that it welds together properly above the bridge 22 to make a good pipe. As explained above, however, a limit to the temperature of extrusion of. binary lead tellurium alloy has been set'l by reason of the coarse structure which develops in the nished pipe. When however a lead tellurium alloy containing from.0. 030.1% 'of copper is used, the pipe maybe extruded vat a high temperature withoaut a coarse structure resulting. This ensures adequate welding together of the pipe. It

the alloy contains above 0.06% copper there is the additional advantage `that local welding of thev finished pipe is-possible without developing a coarse structure in the weld.

It is-a dicult matter to determine the temperatures prevailing in the container of the extrusion pressf and the practice is toestimate them by means of pyrometers inserted into the wall of the container and of the die box.y In my experiments thev ends of the pyrometers extended to a distance.. of one inch from the. metal, and of coursefthe readings are much lower thanthe actual temperatureof. the metal.v In one case in which-extremely:satisfactory extrusion of an alloy containing-0.05% tellurium and 0.067%

copper was r if'btaijned, the'freadings were as fol-v lows:

Degrees centigrade Temperature of. metal in the melting pot, which is charged into the con- The' alloys referred to may also usefully be employed for making cable sheathing, a sample of.which is illustrated in Fig. 7. The electric conductor 30 is covered with insulation 3i and sheathed with a lead alloy coating. The alloy contains 0.05% tellurium and 0.067% copper.

What I claim as my invention and desire to secure by Letters Patent is:-

1. A method of manufacturing an extruded product, which comprises alloying lead with a proportion of from 0.02 to 0.25% of tellurium and from 0.03 to 0.1% of copper, and submitting the alloy to extrusion at temperatures equal to those customarily employed for extruding ordi- 'nary soft lead to obtain a product which has a iine grain structure throughout despite the high extrusion temperature.

2. A method of. manufacturing an extruded product, which comprises alloying lead with a proportion of from 0.02 to 0.25% of tellurium and from 0.06 to 0.07% of copper, and submitting the alloy to extrusion at temperatures equal to those customarily employed for extruding ordinary soft lead to obtain a'product which has a ne grain structure throughout despite the high extrusion temperature, and is capable of being locally welded without structure as a result of fusion.

3. A method of manufacturing an extruded product, Which comprises alloying lead with a proportion of from 0.02 to 0.1% of tellurium and from 0.06 to 0.07% of copper, and submitting the alloy to extrusion at temperatures equal to those customarily employed for extruding ordinary soft lead to obtain a product which has a ne grain structure throughout despite the high introducing a coarse' extrusion temperature, and is capable of, being locally welded without introducing a coarse structure as a result of fusion.

4. An extruded product made'from an alloy consisting preponderatingly of lead and containing from 0.02 to 0.25% of tellurium and from ,lead and has a fine structure throughout, and

can be locally welded without introducing a coarse structure as a result of fusion.

6. An extruded product made from an alloy consisting preponderatingly of lead and contain.- ing from 0.02 to 0.1% of tellurium and from 0;06 to 0.07% of copper, which product has been extruded at temperatures equal to those customarily employed for extruding ordinary soft lead, and has a fine grain structurethroughout,

and can be locally welded without introducing a coarse structure as a result of fusion.

7. The extrusion at temperatures equal to those customarily employed for the extrusion of ordinary soft lead, of a ternary alloy of lead,

tellurium and copper, containing a proportion of tellurium in beneficial amount not exceeding 0.25% and a proportion of Afrom 0.03%-0.1% of copper, whereby an extruded product is obtained having a ne grain structure throughout notwithstanding the high extrusion temperature employed.

BRINLEY JONES. 

